The present invention provides an improvement over subject matter disclosed in our copending application Ser. No. 390,479 filed June 21, 1982, entitled "Lateral Bidirectional Shielded Notch FET". Our copending application discloses lateral power FET structure which is bidirectional, i.e. current can flow in either direction when the device is in the ON state, whereby to afford AC application. Voltage blocking capability is increased by a notch gate structure and a shielding electrode. A notch extends downwardly from a top major surface to separate left and right source regions and left and right channel regions, and direct the drift region current path between the channels around the bottom of the notch. First and second gate electrodes are provided along opposite sides of the notch proximate the channels for controlling bidirectional conduction.
A shielding electrode is insulated between the first and second gate electrodes. In the OFF state, the shielding electrode shields the right notch edge drift region portion from electric field gradients from the left gate electrode. This prevents the left gate electrode from causing attraction of given polarity carriers in the drift region towards the right edge of the notch, which in turn prevents unwanted notch edge drift region depletion and inducement of conduction channels. The shielding electrode likewise shields the left notch edge drift region portion from electric field gradients from the right gate electrode in the OFF state, to prevent unwanted depletion and inducement of conduction channels in the drift region.
The present invention affords optimal utilization of the integrated structure. PN junctions already present in the integrated structure are additionally used to provide the steering diode function for referencing the shielding electrode to the appropriate potential. This eliminates the need for dedicated discrete diodes.